NEW YORK (AP) — The late “Peanuts” creator Charles Schulz was once so infatuated with a young woman 23 years his junior he sent her dozens of romantic letters and drawings of his beloved cartoon characters. Many of the themes of that correspondence made it into his daily comic strips at the time.

Now those love notes from 1970-1971 are being offered for sale at Sotheby’s in New York by the family of Tracey Claudius, who the auction house says is ill at her home near Philadelphia. It’s estimated the notes will fetch $250,000 to $350,000 at the Dec. 14 auction.

Claudius met the cartoonist on March 16, 1970, while accompanying a friend on an interview assignment. She ostensibly came along as a photographer but afterward admitted in a letter to Schulz that it was a chance for her to meet her idol and thank him “for all the enjoyment Charlie Brown and that ‘stupid beagle’ provide me.”

She was 25. The married Schulz was 48. His comic strip ran for nearly half a century.

Schulz died in 2000 at age 77.

There are 44 letters totaling 56 pages, including 22 original drawings of some of the characters, primarily Charlie Brown, Snoopy and Lucy. Many are signed “Sparky,” Schulz nickname.

Sotheby’s says it the most significant collection of correspondence and drawings by Schulz to come to auction.

“He was quite a private and reserved person,” said Selby Kiffer, Sotheby’s head of fine books and manuscripts. “I don’t think he carried on long correspondence with friends and acquaintances. There’s no record in the commercial world and auction records of that.”

Schulz often lovingly writes Claudius’ name in triplicate: “Tracey Tracey Tracey.” One letter comments on Claudius’ “good points,” including being “beepable,” ”huggable” and “buggable” — language he applied to Lucy and Snoopy in later comic strips, like “Lucy playfully beeped Snoopy’s nose” and Snoopy calling himself “buggable and huggable.”

In two letters from 1970 Schulz writes that he must cease calling Claudius because his long-distance phone calls to her had been discovered by his wife. Soon after, he created a strip in which Charlie Brown berated Snoopy for his obnoxious behavior when he’s not allowed to go out “to see that girl beagle.” In subsequent panels, Charlie warns Snoopy “you’d better start behaving yourself” and when Snoopy picks up the telephone, Charlie Brown yells “And stop making those long-distance phone calls.”

He also sent her a dictionary dust jacket filled with comments including “I’m going to return my new dictionary … there are no words to tell you how much I love you.”

In his 2007 book, “Schulz and Peanuts: A Biography,” David Michaelis said Schulz was almost between two marriages when he embarked on the romance with Claudius. The first marriage ended in 1972; he remarried in 1973.

Michaelis said Schulz twice proposed to Claudius but she turned him down for fear of ruining his reputation as one of America’s most loved icons.